Electrolytic cell



Feb. 16, 1937. J. J. MOYNIHAN 2,070,801

ELECTROLYTIC CELL Filed Oct. 7, 1955 Patented Feb. 16, 1937 ELECTROLYTIC CELL John J. Moynihan, Boston, Mass., assignor to Aerovox Corporation, a corporation of New York Application October 7, 1935, Serial No. 43,878

11 Claims.

My present invention relates to electrolytic condensers and is applicable bothto the dry and to the wet type of such condensers.

As conducive to a clear understanding of the invention, it is noted that the use of aluminum or other film-forming metal for the cathode, ordinarily the can or container of a. wet electrolytic condenser has not proved feasible, because in service, the alternating current ripple superposed on the direct current supply, effects film formation on the cathode, with corresponding decrease in efiective capacity of the unit.

Where copper is used for the cathode to avoid such film formation, the cost is greatly increased and the unit in appearance? does not harmonize with the installation of which it is ordinarily a part. Where the can of aluminum or equivalent material is electro-plated with a non-film-iorming metal, such as chromium, vanadium or manganese, while some economy is effected as compared with the cost of copper cans, the'expense is still considerably greater than that of the aluminum can and the operation presents the objection of the plating slowly entering into solution in, the electrolyte and subsequently replating in a' spongy or porous form, with ultimate exposure of the aluminum to the objectionable film-forming action on the cathode.

An object of the present invention is to provide a cathode, suitable for wet electrolytic condensers, which is non-film-forming, sufficiently strong to perform itsfunction mechanically and neutral electrochemically, and with the use of which the otherwise conventional condenser is in nowise impaired in operation, but is of appreciably lower manufacturing cost.

Another object is to provide a dry electrolytic condenser structure at least equal in performance to such structures of approved type, in which all metal parts are made of aluminum, but by which substantial economies in manufacturing cost are attained.

According to the invention, the cathode or can is made of zinc of a high degree of purity, which, however, contains minute proportions of other metals, to impart to the zinc the desired qualities of mechanical strength, ductility and resistance to corrosion. Zinc of the special properties and degree of purity required for the present invention is, nevertheless, quite inexpensive, in fact considerably less costlyper cubic inch than is aluminum, and admits of forming the can by extrusion in the same manner and with substantially the same apparatus as is used for the extrusion of conventional aluminum cans.

Ordinary zinc, as commercially used has been found unsuitable for applicant's purpose due to its susceptibility to extensive corrosion, which .results in mechanical weakening of the container and also in contamination of the electrolyte and impairment of its usefulness. Zinc substantially pure chemically has been found unsuitable, because of its softness and lack of mechanical strength, since it would collapse in ordinary handling.

According to the present invention, the zinc is of purity well in excess of 99 per cent, preferably between 99.8 and 99.85 per cent. The foreign matter used to give the appropriate properties for extrusion and for mechanical strength, yet without danger of corrosion, are iron, cadmium, and lead. It is important that the iron be present in very small quantities, else the metal would be hardened excessively and working thereof rendered diflicult.

I have found that for best results the iron content should not be greater than .01 per cent and preferably in the neighborhood of .007 per cent; the cadmium content. no greater than .07 per cent and preferably about .05 per cent and the lead 'ta.iner occurs without danger of corrosion or galvanic action, substantially as in the case of the aluminum to aluminum bond specified in the prior patent to Georgiev No. 1,789,949. While the invention is substantially set forth in the foregoing, it is exemplified in the drawing and the description hereinafter.

In the drawing;

Fig. 1 is a view in longitudinal cross-section through a wet condenser embodying the inven tion,

Fig. 215 a view similar to Fig. 1 of a dry condenser, and,

Fig. 3 is a perspective view of the condenser roll used in the embodiment of Fig. 2.

Fig. 1 shows the structure of the wet electro lytic condenser of the copending application of Howard E. Rhodes, Serial No. 35,474, filed August 9th, 1935, in which by way of example, the present invention may be used.

The structure comprises an insulating closure plug III for the lower or open end of the can H, which is rolled over as at I! against a compressible gasket l3. The aluminum anode structure A is mounted on a riser N integral with a rod I5 passing through the plug l0 and affixed thereto and the end wall 16 of the can perforated at I5 has a protruding lip I! rolled in over the flange ii of a dome I! housing a perforated rubber vent piece 2|, sealed against the perforated container end I6. The electrolyte 2|, preferably an aqueous solution of borax and borlc acid submerges the anode and establishes electrical contact to the can, which serves as the cathode. The can has a perforated insulating liner 22 to prevent shoIt-circuiting contact with respect to the anode.

The can according to the present invention is made of zinc which may be readily extruded from a fiat slug. The zinc is preferably of purity in excess of 99 per cent, but not chemically pure and includes foreign substances, preferably iron, cadmium and lead in the proportions and for the reasons previously noted. I

In use, minute amounts of zinc from the can may be found in the electrolyte and even in the di-eiectric film on the anode, but these salts are substantially inert, so far as the di-electric film is concerned and do not detract from its mechanical integrity or its electrical properties, the film showing no sign whatsoever of deterioration.

Referring to Figs. 2 and 3, the dry condenser unit also may be of generally conventional gross structure. The condenser roll is made up of anode foil 25, cathode foil 26,, an intervening layer of absorbent gauze or paper 27 and. a layer 27 of gauze or paper is superposed over the cathode, the four or more layers being rolled together. The roll thus made is inserted in the container or can 29 which may be equipped with a vent 39 at the top and with a closure plug 3| genermly similar to that of Fig. 1. The tab 32 of the anode 25 is electrically connected to the head of the terminal screw 33 through the closure'plug 35, while the tab 34 of the cathode may be clamped between the insulating closure plug 38 and the rim of the can 29.

In the-construction set forth, the can is made of the same combination of metals, primarily zinc, as the can of Fig. 1 audits use efiects economy of cost, without countervailing disadvantage as compared to the use of the conventional aluminuin can. Preferably the cathode foil 26 also is made of zinc, with corresponding economy as compared with the use of aluminum.

With the use Oif the same metal, both for the can and the cathode as is preferred, it is seen that the frictional bond of the zinc cathode to the zinc can does not involve any galvanic or corrosive action.

It will thus be seen that there is herein described apparatus in which the several features of this invention are embodied, and which apparatus in its action attains the various objects of the invention and is wellsuited to meet the requirements of practical use.

As many changes could be made in the above construction, and many apparently widely difierent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:-

1. In an electrolytic condenser of the type comprising a film formed anode, complementary metal parts including a cathode and terminal means and an electrolyte intervening between said anode and said cathode, the combination in which one or more of said metal elements other than the anode are of zinc with impurities therein, but at least 99.8 per cent pure.

2. In a wet electrolytic condenser of the type including a spirally wound formed aluminum anode, a body of electrolyte in contact therewith and a terminal structure including an enclosing metal can; the use of zinc having impurities therein, but at least 99.8 per cent pure as the material for said can.

3. A container for an electrolytic cell comprising a cathode can, made of zinc less than 100 per cent but more than 99.8 per cent pure.

4. A container suitable for an electrolytic condenser cell of either the wet or the dry type, said container composed of zinc, at least 99 per cent pure.

5. A container suitable for an electrolytic condenser cell ofeither the wet or the dry type, said container composed of zinc, of purity in excess of 99.8 per cent. 7

6. A container suitable for an electrolytic condenser cell of either the wet or the dry type, said container composed of zinc, of purity in excess of 99 per cent and having impurities therein including iron between .007 and .01 per cent, cadmium between .05 and .07 per cent and lead around .07 per cent.

7. In a dry electrolytic condenser of the type comprising a container, a condenser roll therein including an anode foil of aluminum, a cathode foil and an intervening absorbent layer having electrolyte therein; the use of soft zinc of purity in excess of 99 per cent for the cathode foil.

8. In a dry electrolytic condenser of the type comprising a metal container, an electrolytic condenser roll therein, comprising a formed anode of aluminum, an absorbent insulating sheet having electrolyte carried thereby, and a cathode foil; the use of zinc having a purity in excess of 99 per cent and including not more than .01 per cent of iron as the material of the container.

9. In an electrolytic condenser of the type comprising a metal container, an electrolytic condenser roll therein, comprising a formed anode of aluminum, an absorbent insulating sheet having electrolyte carried thereby and a cathode foil; the use for both said cathode and said container of zinc of purity in excess of 99.8 per cent and with not more than .01 per cent of iron therein.

10. In an electrolytic condenser of the type comprising a metal container, an electrolytic condenser roll therein, comprising a formed anode of aluminum, an absorbent insulating sheet having. electrolyte carried thereby and a cathode foil; the use for both said cathode and said container of zinc having iron content of between .007 and .01 per cent, cadmium content of between .05 and .07 per cent and lead content around .07 per cent. i

11. In an electrolytic condenser of the type comprising a metal container, an electrolytic condenser roll therein, comprising a formed anode of aluminum, an absorbent insulating sheet having electrolyte carried thereby and a cathode foil; the use for both said cathode and said container of zinc having iron content of between .007 and .01 per cent, cadmium content of between .05 and .07 per cent and lead content around .07' per cent, said cathode being bonded to said container.

JOHN J. MOYNIHAN. 

